Re: Smallest Nuc for Winter?
Based on discussions with Joel I attempted to winter over a small four frame nuc last year, and succeeded. They had a poor queen going into winter so they did not build up the fifth frame when I moved them to a five frame box. I re-queened first thing this spring and it became my strongest hive this year. Judicious use of insulation on the outside, and a sugar block under the top cover was all the help I gave them.
Second year, lots of things still to be learned, a bunch of it the hard way.